The Craig Poisoning Mystery (Musaicum Murder Mysteries). Dorothy Fielding

Ronald Craig's death from arsenic poisoning riles up lot of feathers in a small country side with each person having a strong motif! Excerpt: "You say you're going up to town, Bob, as soon as you've left here. Anywhere near Pont Street? Good. Then do you mind wheeling that nearer to me?" The sick man waved a thin, but still brown hand, to where a little writing cabinet, shaped like a miniature roll-top desk, stood on a swing table. «Thanks,» he went on. «Just wait a minute, will you, while I write a note. If you'll drop it in Houghton's letter-box, or hand it in yourself, I shall be much obliged.» He hesitated. «Yourself,» he repeated. «It's most important, and I don't want to wait for the post.»